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(No Model.)

F. C. WATKINS.

v KROTOPHONE. No. 869,377. Patented Sept. 6, 1887.

33% $135 61% tom-mm UNITED STATES PATENT rricn;

FRANK O. \VATKINS, OF PHILADELPHIA, PENNSYLVANIA, ASSIGNOR, BY MESNE ASSIGNMENTS, TO THE UNITED STATES KROTOPHONE COMPANY,

OF NEW' YORK, N. Y.

KROTOPHONE.

SPECIFICATION forming part of Letters Patent No. 369,377, dated September 6, 1887.

Application filed November 15, 1886. Serial No. 218,957. (No model.)

To aZZ whom it may concern:

Be it known that I, FRANK O. VVATKiNs, a citizen of theUnited States, residing at Philadelphia, in the county of Philadelphia and State of Pennsylvania, have invented certain new and useful Improvements in Krotophones; and I do declare the following to beafnll,clear, and exact description of the invention, such as will enable others skilled in the art towhich it appertains to make and use the same, reference being had to the accompanying drawing, and to the letters and figures of reference marked thereon, which forms a part of this specification.

My invention has relation to certain new and useful improvements in the construction of krotophone-receivers, and the object is to provide a simple, reliable, and convenient form of receiver, whereby thevoice will be reproduced as received from the transmitter, thus avoiding all tendency to interruption from foreign influences, such as induced currents and other causes common to that class of receiving-mstruments using a magnet or coil; and to these ends the novelty consists in the peculiar construction and arrangement of the parts of the same, as will hereinafter be more fully described, and particularly pointed out in the claim.

The figure in the drawing is a longitudinal section of my improved krotophone-receiver.

The present invention is designed as an improvement in form upon the patent granted July 6, 1886, to Edward S. Spaulding, No. 345,084.

A is a rigid non-vibrating carbon diaphragm, provided with a central concave recess, a, and B is a metallic diaphragm mounted parallel with and separated from the diaphragm A by a flexible washer, I).

(3 is a carbon ball located in the recess a. and forming a variable contact between the two diaphragrns.

D is the case, and is provided with the usual ear-piece, E, and binding-posts c e, which are respectively in connection with the two diaphragms. Through the medium of the flexible washer b the two diaphragms may be ad justed with reference to each other by tightening or loosening the ear-piece E.

For a complete description of the operation of the instrument, reference may be had to the patentto Spaulding, krotophone, granted July 6, 1886, No. 345,084.

Having thus described my invention, what I claim is- The combination, with the case D E, provided with the diaphragms or disks A B and carbon sphere U, of the flexible ring D, separating said diaphragms or disks, whereby they may be adjusted with reference to each other as set forth.

In testimony whereof I afiix my signature in presence of two witnesses.

FRANK G. WATKINS.

Witnesses:

THOMAS CARRIGK, Enw. KIDD. 

